PROJECT SUMMARY The AESOP Study (Airborne Exposures to Semi-volatile Organic Pollutants) is a community-based participa- tory research study that assesses exposures and body burdens of atmospheric PCBs among an urban cohort of children and their mothers in an area contaminated with legacy PCBs and where dredging of 3.5 million m3 of PCB-laden sediments is now underway. Airborne PCB exposures, plus serum and urine levels of PCBs and metabolites, are assessed and compared to levels in the cohort before the dredging began as well as to a rural Iowa cohort in an area without legacy PCBs. The AESOP Study is identifying the determinants of PCB expo- sures among children and their mothers including exposure levels indoors and out, dietary intake and other exposure pathways. The Study is also determining how we can best monitor exposures and metabolites. The Specific Aims are: 1: Maintain the urban and rural residential cohorts in East Chicago and Columbus Junction and gather demographic, residential, occupational, activity, dietary and baseline health data from subjects; 2: Collect air samples inside and outside at homes and schools and measure congener-specific concentrations of atmospheric PCBs; 3: Collect blood annually from all subjects and measure PCB congeners and congener- specific metabolites in serum samples and report these values to participants; 4: Collect urine from all subjects and measure congener-specific PCB sulfate metabolites and evaluate the efficacy of urine as a biomarker for exposure to lower-chlorinated congeners; and 5: Model exposures and body burdens for the atmospheric PCB congeners from the cohorts and compare modeled and measured data. These aims are facilitated by strong community support garnered through our Community Engagement Core and aided by sample analyses performed in our Analytical Core. The AESOP Study employs bilingual community-based field staff and has enrolled and followed 264 subjects in these racially and ethnically diverse communities (59% Hispanic, 23% Black, 18% other) and provided new insight into airborne exposures and resulting body burdens. Exposures have been assessed through repeated air sampling inside and outside of homes of subjects and at their local schools and also through annual blood collection and assay for PCB congener and metabolite profiles. The AESOP Study provides human samples and data to other components of the Iowa Superfund Research Program providing enhanced relevance. In this renewal cycle, we will evaluate in greater detail the diet of our subjects using established methodology. This dietary information will be used along with inhalation data and activity logs for integrated exposure modeling. The AESOP Study has changed prevailing views on how most Americans are exposed to PCBs. We have demonstrated that our subjects have substantial exposure to PCB congeners from inhalation in addition to ingestion and their blood shows enrichment with inhaled lower- chlorinated congeners. This has important implications for children's environmental health.